/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */
package org.apache.causeway.persistence.jdo.spring.support;

import javax.jdo.PersistenceManager;
import javax.jdo.PersistenceManagerFactory;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.dao.DataAccessException;
import org.springframework.transaction.support.TransactionSynchronizationManager;
import org.springframework.ui.ModelMap;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.context.request.WebRequestInterceptor;

import org.apache.causeway.persistence.jdo.spring.integration.PersistenceManagerFactoryUtils;
import org.apache.causeway.persistence.jdo.spring.integration.PersistenceManagerHolder;

/**
 * Spring web request interceptor that binds a JDO PersistenceManager to the
 * thread for the entire processing of the request. Intended for the "Open
 * PersistenceManager in View" pattern, i.e. to allow for lazy loading in
 * web views despite the original transactions already being completed.
 *
 * <p>This interceptor makes JDO PersistenceManagers available via the current thread,
 * which will be autodetected by transaction managers. It is suitable for service
 * layer transactions via {@link org.apache.causeway.persistence.jdo.spring.integration.JdoTransactionManager}
 * or {@link org.springframework.transaction.jta.JtaTransactionManager} as well
 * as for non-transactional read-only execution.
 *
 * <p>In contrast to {@link OpenPersistenceManagerInViewFilter}, this interceptor
 * is set up in a Spring application context and can thus take advantage of
 * bean wiring.
 *
 * @see OpenPersistenceManagerInViewFilter
 * @see org.apache.causeway.persistence.jdo.spring.integration.JdoTransactionManager
 * @see org.apache.causeway.persistence.jdo.spring.integration.PersistenceManagerFactoryUtils#getPersistenceManager
 * @see org.springframework.transaction.support.TransactionSynchronizationManager
 */
public class OpenPersistenceManagerInViewInterceptor implements WebRequestInterceptor {

	/**
	 * Suffix that gets appended to the PersistenceManagerFactory toString
	 * representation for the "participate in existing persistence manager
	 * handling" request attribute.
	 * @see #getParticipateAttributeName
	 */
	public static final String PARTICIPATE_SUFFIX = ".PARTICIPATE";


	protected final Log logger = LogFactory.getLog(getClass());

	private PersistenceManagerFactory persistenceManagerFactory;


	/**
	 * Set the JDO PersistenceManagerFactory that should be used to create
	 * PersistenceManagers.
	 */
	public void setPersistenceManagerFactory(PersistenceManagerFactory pmf) {
		this.persistenceManagerFactory = pmf;
	}

	/**
	 * Return the JDO PersistenceManagerFactory that should be used to create
	 * PersistenceManagers.
	 */
	public PersistenceManagerFactory getPersistenceManagerFactory() {
		return persistenceManagerFactory;
	}


	@Override
	public void preHandle(WebRequest request) throws DataAccessException {
		if (TransactionSynchronizationManager.hasResource(getPersistenceManagerFactory())) {
			// Do not modify the PersistenceManager: just mark the request accordingly.
			String participateAttributeName = getParticipateAttributeName();
			Integer count = (Integer) request.getAttribute(participateAttributeName, WebRequest.SCOPE_REQUEST);
			int newCount = (count != null ? count + 1 : 1);
			request.setAttribute(getParticipateAttributeName(), newCount, WebRequest.SCOPE_REQUEST);
		}
		else {
			logger.debug("Opening JDO PersistenceManager in OpenPersistenceManagerInViewInterceptor");
			PersistenceManager pm =
					PersistenceManagerFactoryUtils.getPersistenceManager(getPersistenceManagerFactory(), true);
			TransactionSynchronizationManager.bindResource(
					getPersistenceManagerFactory(), new PersistenceManagerHolder(pm));
		}
	}

	@Override
	public void postHandle(WebRequest request, ModelMap model) {
	}

	@Override
	public void afterCompletion(WebRequest request, Exception ex) throws DataAccessException {
		String participateAttributeName = getParticipateAttributeName();
		Integer count = (Integer) request.getAttribute(participateAttributeName, WebRequest.SCOPE_REQUEST);
		if (count != null) {
			// Do not modify the PersistenceManager: just clear the marker.
			if (count > 1) {
				request.setAttribute(participateAttributeName, count - 1, WebRequest.SCOPE_REQUEST);
			}
			else {
				request.removeAttribute(participateAttributeName, WebRequest.SCOPE_REQUEST);
			}
		}
		else {
			PersistenceManagerHolder pmHolder = (PersistenceManagerHolder)
					TransactionSynchronizationManager.unbindResource(getPersistenceManagerFactory());
			logger.debug("Closing JDO PersistenceManager in OpenPersistenceManagerInViewInterceptor");
			PersistenceManagerFactoryUtils.releasePersistenceManager(
					pmHolder.getPersistenceManager(), getPersistenceManagerFactory());
		}
	}

	/**
	 * Return the name of the request attribute that identifies that a request is
	 * already filtered. Default implementation takes the toString representation
	 * of the PersistenceManagerFactory instance and appends ".FILTERED".
	 * @see #PARTICIPATE_SUFFIX
	 */
	protected String getParticipateAttributeName() {
		return getPersistenceManagerFactory().toString() + PARTICIPATE_SUFFIX;
	}

}
